The invention relates to a circuit arrangement for measured value detection, transfer and analysis, with a measured value detection section, a measured value analyzing section and a connection consisting only of a outgoing conductor and a return conductor between the measured value detection section and the measured value analyzing section, in connection with which the measured value detection section has a measured value recorder, a measuring transformer circuit, a switch controller connected upstream from the measuring transformer circuit and a current regulator connected upstream from the switch controller, in connection with which the measured value analyzing section has a voltage source and an analyzing circuit, and the switch controller delivers a constant operating voltage for the measuring transformer circuit, and the current regulator, controlled by the measuring transformer circuit, sets a measured value and power supply current flowing through the outgoing conductor and the return conductor and representing the measured value.
Circuit arrangements of the kind being discussed are known in many instances (cf. e.g. German Patent 39 34 007, Europe Patent Disclosure 0,744,724 and German Patent Disclosure 197 23 645). For these circuit arrangements, it is essential that the connection between the measured value detection section and the measured value analyzing section consists of only two conductors and that a current flows through these two conductors that represents the measured value and also serves to supply electric power to the measured value detection section; the current flowing through the two conductors was thus designated in the introduction as measured value and power supply current.
Circuit arrangements of the kind in question are often conceived and designed in such a way that the voltage source in the measured value analyzing section is a direct voltage source, so the measured value and power supply current is a direct current. These circuit arrangements are also frequently conceived and designed in such a way that the measured value and power supply current represents the measured value between a lower limit value, namely 4 mA and an upper limit value, namely 20 mA; the lower limit value of 4 mA thus represents the smallest measured value and the upper limit value of 20 mA the greatest measured value (cf. German Patent 39 34 007, Page 2, Lines 19 through 24).
It will be taken as a basis throughout the following that the circuit arrangement in question is of the kind in which the voltage source provided in the measured value analyzing section is a direct voltage source, and the measured value and power supply current is thus a direct current. That is also why the connection between the measured value detection section and the measured value analyzing section was already described as consisting of an outgoing conductor and a return conductor. In addition, the technical current direction will be taken as a basis throughout the following; in an electric circuit connected to a direct voltage source, the direct current thus flows from the plus pole of the direct voltage source via the electric circuit to the minus pole of the direct voltage source.
The section of the circuit arrangement in question that is designated above and in the following as the measured value and power supply current is also referred to as the transmitter station (cf. German Patent 39 34 007) or as sending point (cf. European Patent Disclosure 0,744,724 and German Patent Disclosure 197 23 645), while the section of the circuit arrangement in question that is designated here as the measured value analyzing section is also referred to as the receiving station (cf. German Patent 39 34 007) or as receiving point (cf. European Patent Disclosure 0,744,724 and German Patent Disclosure 197 23 645). The connection, consisting of an outgoing conductor and a return conductor according to the terminology used here, between the measured value detection section and the measured value analyzing section is also referred to as a two-wire circuit station (cf. German Patent 39 34 007, European Patent Disclosure 0,744,724 and German Patent Disclosure 197 23 645).
Since the measured value currentxe2x80x94representing the measured valuexe2x80x94in the circuit arrangements concerned in this instancexe2x80x94as a rule, ranging from 4 mA to 20 mA as illustratedxe2x80x94is also the supply current for the measured value detection section, the electric power available for the measured value detection section is limited by the lower limit value of the measured value and power supply current, i.e., by 4 mA as a rulexe2x80x94which is often problematic (cf. German Patent 39 34 007, Page 2, lines 25 through 42).
In the circuit arrangement in question, the measuring transformer circuitxe2x80x94with the related measured value recorderxe2x80x94is actually the most important part in terms of function. Since the signal-to-noise ratio and the dynamic characteristics of the measuring transformer circuit depend on the power available for the measuring transformer circuit, the technical problem on which the invention is based is to optimize the power available for the measuring transformer circuit.